Which of the following is a plant hormone?

Gibberellin

The correct answer is Option (2) – Gibberellin

Gibberellins are the plant growth regulators involved in regulating the growth and influencing different developmental processes which include stem elongation, germination, flowering, enzyme induction, etc.

Gibberellins have different effects on plant growth and the stem elongation is the most dramatic amongst all.

The internodes grow so long that the plants become indistinguishable from climbing. The Gibberellins overcome the genetic limitations in different dwarf varieties.

There are more than 70 gibberellins isolated. They are GA1, GA2, GA3 and so on. GA3 Gibberellic acid is the most widely studied plant growth regulators. 

Prolactin , Insulin  and oxytocin are hormones produced in human body .